// 单例模式在TS中的应用
{
  class Axios {
    // 此时constructor无法在外部通过new调用
    private static instance: Axios | null = null
    private constructor() {
      // console.log('构造函数');
    }

    static make(): Axios {
      if (this.instance === null) {
        console.log('创建实例');

        Axios.instance = new Axios()
      }
      return Axios.instance
    }
  }
  const instance = Axios.make()
  Axios.make()

}